The present invention relates to gas turbines and, more particularly, to gas turbines employed for chemical processing.
Gas turbines are well known for their use in the production of mechanical energy which may be applied to such tasks as vehicle propulsion or power generation. Gas turbines normally burn fuel in an open cycle in which air is compressed in a compressor, then heated by burning fuel in a combustor. The heated air and products of combustion are impinged on blades of one or more turbine wheels before being exhausted to the atmosphere. The turbine wheels are rotated by the energetic hot gases and the rotational energy is coupled to a load as well as back to the compressor.
In my prior U.S. patent application Ser. No. 263,316, filed May 13, 1981, I disclosed a closed-cycle gas turbine system in which pure oxygen, fed to the combustor together with fuel and recycled exhaust from the turbine, produces a relatively high percentage of carbon dioxide in this closed system. A part of the exhaust stream is bled off to maintain the internal inventory of materials constant in the closed system and the carbon dioxide in the bled off portion is recovered for chemical or industrial use. Excess energy from the gas turbine is employed to generate electric power as an economic output commodity. Heat from the gas turbine exhaust is recovered in a heat recovery steam generator to be used either for the generation of additional electric power or as an economic commodity itself.
One of the drawbacks of my above-referenced patent application is the need for a plant producing pure oxygen. Such an oxygen plant typically separates the two principal constituents in the air, namely oxygen and nitrogen, and delivers the oxygen to the gas turbine compressor. If the nitrogen is also recovered and sold or used, its value may at least partly justify the capital and operating expense of the oxygen plant. However, if the plant location is far from a market for nitrogen, as is often the case in such applications as oil field tertiary recovery, the capital and operating cost of the oxygen plant is a negative factor on the overall economic viability of the project.
One prior public use is known in which the compressor of an open-cycle gas turbine supplies a portion of its compressed air to a chemical process in which the oxygen in the air is removed and the remaining nitrogen is returned to a central portion of the combustor. The remainder of the compressed air from the compressor is fed to the combustor as combustion air in the vicinity of fuel injection and the nitrogen effluent of the chemical process is added to the combustion gas stream as cooling and dilution fluid downstream of the combustion area.